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Tuesday, 21 August 2012

What is Change Data Capture and How to validate CDC in Obia?

Change Data Capture in
Datawarehose identifies the data that
has been added,removed and updated.Instead of using the difficult techniques
what it dose is it captures the change data resulting from INSERT, UPDATE, and DELETE operations made to user tables And this
change data is then stored in a relational table called a change table.This is
how CDC works.

Data warehousing deals with a lot of extraction and
transportation of data from source database to the datawarehouse. Change Data
Capture identifies and processes only the data that has changed and makes the
change data available for further use.

Advantages of capturing change data
with Change Data Capture:

Compared to techniques like Table
differencing(All data
from old_version table MINUS All data
FROM new_version table )and
Change-valueselection(capturing
the data on the source database by selecting the new and changed data from the
source tables based on the cols like Last update date) this technique is far more easy and less
complicated.

Captures
all the data:Change Data
Capture can capture all effects of INSERT, UPDATE, and DELETE operations even the changes before and
after .

Cost: Compared to other techniques CDC is far
less expensive

Performance
:Asynchronous Change
Data Capture can be configured to have minimal performance impact on the source
database.

How to validate Change Data Captured?

Change Data Capture objects are exported
and imported as part of full database export and import (exp and imp)operations
into the Datawarehouse.After the import operation Change Data Capture objects
are validated to determine if all expected underlying objects are present in
the correct form. Change Data Capture generates validation warnings in the
import log if it detects validation problems. Imported Change Data Capture
objects with validation warnings usually cannot continue capturing change data.